The present disclosure relates to a control device and method for a diesel engine.
Japanese Unexamined Patent Publication No. 2013-185540 discloses an example of a control device for a diesel engine. This engine includes a fuel-injector (injector) that is configured to inject fuel into a combustion chamber, and a supercharger (turbocharger) that is configured to supercharge gas to be introduced into the combustion chamber.
The control device according to the above-described Japanese Unexamined Patent Publication No. 2013-185540 controls an injection mode of the fuel through the fuel-injector to execute main injection that allows injected fuel to start combusting from near a compression top dead center, and pilot injection that is performed to cause preliminary combustion (pre-combustion) to preheat the interior of a cylinder before the combustion based on that main injection.
Meanwhile, superchargers including turbochargers may cause a delay in reduction in a supercharging pressure due to inertia of a turbine and other factors, for example, when an attempt is made to reduce the supercharging pressure in accordance with reduction in the degree of opening of an accelerator pedal. In that case, there is a risk of an excessive rise in the cylinder pressure because of a combination of a steep progress in the combustion based on the pilot injection and the combustion based on the main injection.
Thus, the control device according to the above-described Japanese Unexamined Patent Publication No. 2013-185540 retards the start timing of each of the pilot injection and the main injection, thereby slowly progressing the combustion based on each of the injections to reduce the cylinder pressure.
As a result of earnest investigation, the present inventors have prevented excessive rise in a cylinder pressure, and consequently enhanced silence of engines, by an approach different from the technique disclosed in the above-described Japanese Unexamined Patent Publication No. 2013-185540.
It is therefore an object of the present disclosure to enhance silence of an engine using a control device and method for a diesel engine.